The present invention relates generally to the use of fluorescent tracers to determine, analyze and quantify fluid movement, fluid dilution and fluid removal. Specifically, the invention relates to the use of quantum-sized particles to determine, analyze and quantify fluid movement, fluid dilution and fluid removal. The present invention further relates to methods for monitoring and quantifying the amounts of solid materials dissolved in a liquid.
Quantum-sized particles, i.e., those having diameters within the range of about 0.1 nm to about 50 nm, also known as quantum dots or nanocrystals, are known for the luminescent properties that they possess due to their small size, large surface area and optico-electronic properties. Luminescent nanocrystals have been shown to be useful as detectable labels for applications such as oligonucleotide tags, tissue imaging stains, protein expression probes, and in the detection of biological compounds both in vitro and in vivo.
Typically the transfer of fluid was determined by employing an organic dye or measuring the flow of fluid past an injector. One drawback of organic dyes is the deterioration of fluorescence intensity upon prolonged and/or repeated exposure to excitation light. This fading, called photobleaching, is dependent on the intensity of the excitation light and the duration of the illumination. In addition, conversion of the dye into a non-fluorescent species is irreversible. Furthermore, the degradation products of dyes are organic compounds which may interfere with the composition being examined. Moreover, at high concentrations organic dyes self absorb, limiting their linear dynamic range.
Another drawback of organic dyes is a spectral overlap which exists from one dye to another. This is due in part to the relatively wide emission spectra of organic dyes and the overlap of the spectra near the tailing region. In addition, low molecular weight dyes may be impractical for some applications because they do not provide a bright enough fluorescent signal. The ideal fluorescent label should fulfill many requirements. Among the desired qualities are the following: (i) high fluorescent intensity (for detection in small quantities), (ii) a separation of at least 50 nm between the absorption and fluorescing frequencies, (iii) solubility in the test composition, (iv) stability towards harsh conditions and high temperatures, (v) a symmetric emission lineshape for easy analysis, (vi) uniform dispersion in the test composition; (vii) compatibility with automated analysis; (viii) inherently large dynamic range with minimal self quenching; and (ix) being chemically inert with respect to the active components making up the fluid being monitored.
The differences in the chemical properties of standard organic fluorescent dyes make multiple, parallel assays quite impractical since different chemical reactions may be involved for each dye used in the variety of applications of fluorescent labels. Furthermore, the differences in the chemical properties of standard organic fluorescent dyes make multiple, parallel assays impractical as different chemical reactions may be involved for each dye used in the variety of applications of fluorescent labels.
Moreover, there are chemical and physical limitations to the use of organic fluorescent dyes. One of these limitations is the variation of excitation wavelengths of different colored dyes. As a result, simultaneously using two or more fluorescent tags with different excitation wavelengths requires multiple excitation light sources. This requirement thus adds to the cost and complexity of methods utilizing multiple fluorescent dyes. Moreover, organic dyes exhibit quenching of fluorescence at even moderate concentrations, leading to significant non-linear dilution effects.
A drawback of measuring the flow of fluid past through an injector is that this method is not capable of verifying that the fluid has actually been delivered to the desired device or receptacle.
Thus, there is a need in the art for a fluorescent label that satisfies the above-described criteria for use in systems where one or more fluids are transferred and which is able to verify and quantify the addition of fluid to a reactor vessel or the like.